Not much to see here, just a dog running across the water of a swimming pool.
To be serious, this dog either is running fast enough over the water to not sink in (unlikely), or there are other forces at work.
Looking closely, it appears there's some sort of net or covering on top of the water, so it's likely that's how the dog can run across.
Then again, the dude's reaction seems like the reaction of someone who just saw a dog run across some water.
Hmmm...